Terahertz pulse generation from relativistic laser wakes in axially magnetized plasmas

Using multidimensional particle-in-cell simulations, we demonstrate the generation of >30GVm^{−1} terahertz (THz) fields by relativistic, few-femtosecond laser pulses interacting with gas plasmas embedded in >100T magnetic fields parallel to the laser path. Parameter scans in the laser and magnetic field strengths predict laser-to-THz conversion efficiencies in excess of 2×10^{−3} in the highly relativistic, strong-magnetization regime. The simulation results are interpreted in light of a perturbative quasistatic model, revealing that the dominant azimuthal THz field is driven by transverse gradients in the longitudinal laser wakefield. Generation of an additional, radially polarized THz field is also foreseen at high magnetization levels as confirmed by numerical simulations.